IsolatedStorageTarget - minor bug fixes

NOTE: You can ignore the csproj files, I just included the IsolatedStorageTarget files in my proj.

Minor fixes, enough to get the tests to pass.

- Check if a file exist before deleting, otherwise IsolatedStorageFile will throw an error
- IsolatedStorageFile.MoveFile() doesn't throw an IOException, instead a IsolatedStorageException
- Sequential archive internal dictionary didn't have the full name (Line 796)